Senate Democrats facing difficult reelections are breaking with President Obama’s endorsement of same-sex marriage, a sign the issue is politically dangerous in battleground states.

Sens. Jon Tester (Mont.) and Claire McCaskill (Mo.), the two most vulnerable Democratic senators, have declined to endorse Obama’s call for the legalization of gay marriage.

Sens. Joe Manchin (W.Va.), Bob Casey (Pa.) and Bill Nelson (Fla.), Democrats who have easier races but in states that could become more competitive by November, have also backed away from Obama’s stance.

They all represent states with constitutional amendments or laws banning same-sex marriage.